Projecting a sketch onto a sphere

david_kurtz

A student of mine is trying to make R2D2.  They would like to extrude a projection of a rectangle off a sphere. 

The wrap tool does not like spheres.  The projected curve is the tool that I like to suggest (by name only), but that does not do it either.  

Does anyone have suggestions for how to project a rectangle onto a curved surface, like a sphere?   

steve_shubin

@david_kurtz

Here is one way

Once you have your basic R2-D2 shape, this takes three steps to do

https://cad.onshape.com/documents/9f6addd180c1ed94b3c0a273/w/fdedd101664e09e8716051e8/e/877725751bb4fd611825ad09

david_kurtz

@steve_shubin Thank you! That is very helpful.  

steve_shubin

@david_kurtz

With 3 more steps (features), I would begin to form things like a lens

https://cad.onshape.com/documents/9f6addd180c1ed94b3c0a273/w/fdedd101664e09e8716051e8/e/877725751bb4fd611825ad09

steve_shubin

@david_kurtz

But, if I remember correctly, not long ago, maybe a couple weeks ago at the most, it was either @Evan_Reese or @konstantin_shiriazdanov that came up with either a Wrap that worked on more than cylinders. Or maybe it was an unfold that worked on organic shapes.

But if it was a wrap that worked on more than just cylinders or cones, then that could really help in your case because you can get by (for the most part) with ONE sketch, and then just do a number of thickens or extrudes 

EvanReese

Definitely wasn't me. That's way over my head. Sketch Wrapper is the one I think you're thinking of from @konstantin_shiriazdanov not sure if it can do spheres or not.

EvanReese

I think this is how I'd approach it though. Since it's a half dome, all of the edges are visible from the top view, so you can just project one sketch and use a few native features to bump them out and clean up the extra edges. It may take a little bit of eyeballing, if that's acceptable here. Make sure all of the radial lines are made coincident with the origin so they appear vertical when split. Here's the example doc shown below.

konstantin_shiriazdanov

I think what @Evan_Reese did is the best for this untill you only need concentric and radial lines on the sphere. Sketch wrapper wouldn't help here since it doesn't support spherical surfaces.

david_kurtz

@Evan_Reese
Your solution is more of what I had imagined.  Thank you! 

@konstantin_shiriazdanov, @steve_shubin - Thank you for the quick replies and solutions!
It's great to post a question and hear back with multiple answers in just a few hours.

steve_shubin

@david_kurtz
@Evan_Reese
@konstantin_shiriazdanov

I like Evan’s ONE sketch solution. Nice overhead, ‘Plan View’ 👍

David — depending how detailed you want to get, there may be times where you may find you do have to use Wrap to Cylinder, in conjunction with loft to centerpoint of hemisphere, or extrude to surface

By the way, I did find what it was that I mentioned previously. But it was not a wrap, but rather an unfold of something other than a cylinder or a cone that Konstantin did

https://cad.onshape.com/documents/51b2c9ee60d78d9f27118b90/w/6b41eb019eb71fbb58073cc5/e/d74d14c27c0f262d62d40dfd